Radio (Encyclopedia of Science)
Radio is the technology that allows information to be transmitted and received over radio waves. Radio makes it possible to establish wireless two-way communication between individual pairs of transmitters/receivers and it is used for one-way broadcasts to many receivers. Radio signals can carry speech, music, or digitally encoded entertainment. Radio waves occur naturally in space or can be created by people. They are a long-wave form of electromagnetic radiation, or radiation that transmits energy through the interaction of electricity and magnetism.
The history of radio
In the nineteenth century, Scottish physicist James Clerk Maxwell (1831879) developed a mathematical theory proving that magnetism and electricity were related. His theory linking the two forces became known as the electromagnetic theory. He predicted that light is only one type of electromagnetic radiation and that wavelengths should exist below infrared (those situated outside the visible spectrum at the red or long-wavelength end) and above ultraviolet (situated outside the visible spectrum at the violet or short-wavelength end). In the 1880s, German physicist Heinrich Hertz (1857894) discovered extremely long-wavelength radio waves, proving Maxwell's theory.
Italian physicist and engineer Guglielmo Marconi (1874937), fascinated with Hertz's discovery of radio waves, built...
(The entire section is 785 words.)
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Radio (Encyclopedia of Public Health)
Radio is looked at as an important tool in educating the general public about health issues. In particular, it is believed that properly developed community radio can encourage community-driven problem solving. At the government level, radio has been used to advise the public on issues such as new health standards and seasonal food warnings.
Examples of radio's role in education and public health awareness are numerous. Sound Partners program run by the Benton Foundationrovides grants to public radio stations interested in developing community-oriented educational content for the good of public health. Many talk-radio stations and public broadcasters feature special call-in medical programming and general health information. Public addresses via radio, such as President Clinton's radio talk on May 6, 2000, on food safety, and the radio dissemination of automotive product recalls by the United States National Highway Traffic Safety Administration, also exhibit the effectiveness of radio as a means of informing the public.
While the above services are good for the general public, physicians need to be educated in a different manner. Internet radio involves broadcasting audio content on the Internet so it can be heard anywhere in the world through a computer or WebTV unit. Examples of Internet radio delivery systems include RealNetwork's RealPlayer and Microsoft's Windows Media Player.
Internet radio is important for the public health and medical community because it creates an opportunity for high-quality interactive distance learning and education without geographic limitations. For example, in a normal educational setting doctors would need to go to a special class or conference to educate themselves. Internet radio can provide doctors with an alternative to the traditional continuing education setting.
(SEE ALSO: Mass Media; Mass Media and Tobacco Control; Media Advocacy)
Radio (Genocide and Crimes Against Humanity)
Radio was one of the great forces behind social and political mobilization in the twentieth century. Joseph Goebbels, one of Adolf Hitler's earliest and most enthusiastic supporters, understood the potential power of this media. When Hitler rose to power in 1933, he appointed Goebbels as his minister of propaganda; in this role, the latter displayed his talents, particularly where radio broadcasts were concerned. Under Goebbels's leadership the Nazis subsidized the production and distribution of millions of cheap radios in order to strengthen their grip on the population. Goebbels's first radios were deliberately designed with a limited range so that they would not pick up foreign transmissions. At the beginning of World War II over 70 percent of all German households owned a radio, the highest percentage in the world.
The extent to which Nazi radio broadcasts played a clear role in preparing and then swaying German public opinion toward the extermination of the Jews is hard to evaluate. Like the press or cinema, radio was one of the media used to diffuse anti-Semitic themes. In the early years of the Nazi regime the radio called for a boycott of Jewish shops. However, not a single radio program with a specific theme of anti-Semitism was designed. Entertainment programs did not include such messages. Of course, speeches given by Hitler and other Nazi leaders containing angry passages condemning the Jews were routinely broadcast on the radio. On the eve of Kristallnacht (Night of broken glass) on November 9, 1938, Goebbels used the radio to urge the German public to pillage Jewish shops and burn down synagogues. During World War II the Nazi media repetitively depicted Jews as devilish characters responsible for the soon worldwide conflict but they continued to keep their extermination a secret.
Some fifty years later the radio was used in a much more direct way to set the stage for and then perpetrate genocide in Rwanda. Within the context of civil war, initiated in October 1990 by the Tutsi-dominated Rwanda Patriotic Front (RPF), Hutu extremists decided to create their own radio station. Their intention had been to counteract the RPF broadcasts (Radio Muhabura) and those of the official national station (Radio Rwanda) the latter was indeed considered too moderate and had simply become an outlet for the new multiparty government by 1992. This project, driven by the historian Ferdinand Nahimana who had been dismissed from the Rwandan Office of Information (ORINFOR) that supervised Radio Rwanda, commenced in April 1993 with the creation of Radio Télévision Libre Mille-Collines. This new station was formally independent, but in fact influential politicians belonging to the president's entourage, some of them related by marriage, supported it. As in Nazi Germany, many cheap radio receivers were distributed to the population in different regions of the country. Starting in August 1993 the station broadcast rousing Zairian music popular among Rwandans, and the station became rapidly renowned. RTLM presented itself as an interactive radio station, giving listeners the opportunity to speak to the Hutu people by calling into the station.
This broadcasting format was new to Rwanda at that time. RTLM attracted the populace with its candor and humor, but its ideological message was clear: It was the voice of the Hutu people, victims of the profiteering elites, of calculating Tutsis and those who betrayed the Hutu cause. After the Hutu president of Burundi, Melchior Ndadaye, was killed on October 21, 1993, RTLM programming became still more aggressive. All day long the station repeated a political jingle that prompted its audience to wait: "We have hot news," the broadcasters would proclaim, and when the news was finally diffused, listeners would hear a series of vicious anti-Tutsi slogans. Several times a day the station also broadcast songs written by the Hutu extremist Simon Bikindi.
Immediately after the assassination of the Rwandan president, Juvenal Habyarimana, on April 6, 1994, RTLM openly called for the massacre of Tutsis, Hutu opponents, and even Belgian peacekeepers. Hutu extremists used their radio station to ridicule those in the local administration who called for calm. From April to June 1994 RTLM helped mobilize the Hutu population in support of the killing of the Tutsi minority. The radio station even dared to name the Tutsis who remained to be killed. For the first time in history radio was used to directly perpetrate genocide.
The role of radio in the killings must not be overestimated, however. Numerous massacres were committed without the direct influence of RTLM. Military officers, militia leaders, and mayors who supervised Hutu peasants on the ground played a crucial role in organizing the population to kill. Nevertheless, it is evident that radio, the main media in a country where newspapers are hardly read and television remains in short supply, played an important role in the diffusion of racist anti-Tutsi ideology. RTLM provided Hutu extremists with a useful communications tool that reinforced their political influence over the people. Radio can be a most formidable weapon, in particular when introduced to a population already weakened by fear. Words conveyed over the radio may thus turn deadly.
SEE ALSO Incitement; Propaganda; Radio Télévision Libre Mille-Collines; Rwanda; Television
Chalk, Frank (1999). "Hate Radio in Rwanda." In The Path of a Genocide, ed. Howard Adelman and Astri Suhrke. New Brunswick, N.J.: Transaction Publishers.
Chrétien, Jean-Pierre, ed. (1995). Rwanda. Les médias du génocide. Paris: Karthala.
Marszolek, Inge (1998). Zuhoeren und Gehoertwerden. Vol. 1: Radio im Nationalsozialismus, ed. Adelheid von Saldern. Tuebingen: Diskord.
Radio (How Products are Made)
The radio receives electromagnetic waves from the air that are sent by a radio transmitter. Electromagnetic waves are a combination of electrical and magnetic fields that overlap. The radio converts these electromagnetic waves, called a signal, into sounds that humans can hear.
Radios are a part of everyday life. Not only are they used to play music or as alarms in the morning, they are also used in cordless phones, cell phones, baby monitors, garage door openers, toys, satellites, and radar. Radios also play an important role in communications for police, fire, industry, and the military. Although there are many types of radioslock, car, amateur (ham), stereoll contain the same basic components.
Radios come in all shapes and sizes, from a little AM/FM "Walkman" to a highly sophisticated, multi-mode transceiver where both the transmitter and receiver are combined in one unit. The most common modes for a broadcast radio are AM (amplitude modulation) and FM (frequency modulation). Other modes used by ham radio operators, industry, and the military are CW (continuous wave using Morse code), SSB (single sideband), digital modes such as telemetry, radio teletype, and PSK (phase shift keying).
Guglielmo Marconi successfully sent the first radio message across the Atlantic Ocean in December 1901 from England to Newfoundland. Marconi's radio did not receive voice or music. Rather, it received buzzing sounds created by a spark gap transmitter sending a signal using Morse code.
The radio got its voice on Christmas Eve 1906. As dozens of ship and amateur radio operators listened for the evening's traffic messages, they were amazed to hear a man's voice calling "CQ, CQ" (which means calling all stations, I have messages) instead of the customary dits and dahs of Morse code. The message was transmitted by Professor Reginald Aubrey Fessenden from a small radio station in Brant Rock, Massachusetts.
In the years from 1904 to 1914, the radio went through many refinements with the invention of the diode and triode vacuum tubes. These devices enabled better transmission and reception of voice and music. Also during this time period, the radio became standard equipment on ships crossing the oceans.
The radio came of age during World War I. Military leaders recognized its value for communicating with the infantry and ships at sea. During the WWI, many advancements were made to the radio making it more powerful and compact. In 1923, Edwin Armstrong invented the superhetrodyne radio. It was a major advancement in how a radio worked. The basic principles used in the superhetrodyne radio are still in use today.
On November 2, 1920 the first commercial radio station went on the air in Pittsburgh, Pennsylvania. It was an instant success, and began the radio revolution called the "Golden Age of Radio." The Golden Age of Radio lasted from the early 1920s through the late 1940s when television brought in a whole new era. During this Golden Age, the radio evolved from a simple device in a bulky box to a complex piece of equipment housed in beautiful wooden cabinets. People would gather around the radio and listen to the latest news and radio plays. The radio occupied a similar position as today's television set.
On June 30, 1948 the transistor was successfully demonstrated at Bell Laboratories. The transistor allowed radios to become compact, with the smallest ones able to fit in a shirt pocket. In 1959, Jack Kilby and Robert Noyce received the first patent for the integrated circuit. The space program of the 1960s would bring more advances to the integrated circuit. Now, a radio could fit in the frame of eyeglasses or inside a pair of small stereo earphones. Today, the frequency dial printed on the cabinet has been replaced with light emitting diodes or liquid crystal displays.
Today's radio consists of an antenna, printed circuit board, resistors, capacitors, coils and transformers, transistors, integrated circuits, and a speaker. All of these parts are housed in a plastic case.
An internal antenna consists of small-diameter insulated copper wire wound around a ferrite core. An external antenna consists of several aluminum tubes that slide within one another.
The printed circuit board consists of a copper-clad pattern cemented to a phenolic board. The copper pattern is the wiring from component to component. It replaces most of the wiring used in earlier radios.
Resistors limit the flow of electricity. They consist of a carbon film deposited on a cylindrical substrate, encased in a plastic (alkyd polyester) housing, with wire leads made of copper.
Capacitors store an electrical charge and allow alternating current to flow through an electrical circuit but prevent direct current from flowing in the same circuit. Fixed capacitors consist of two extended aluminum foil electrodes insulated by polypropylene film, housed in a plastic or ceramic housing with copper wire leads. Variable capacitors have a set of fixed aluminum plates and a set of rotating aluminum plates with an air insulator.
Coils and transformers perform similar functions. Their purpose is to insulate a circuit while transferring energy from one circuit to another. They consist of two or more sets of copper wire coils either wound on an insulator or mounted side-by-side with air as the insulator.
Transistors consist of germanium or silicon encased in a metal housing with copper wire leads. The transistor controls the flow of electricity in a circuit. Transistors replaced vacuum tubes used in earlier radios.
The integrated circuit houses thousands of resistors, capacitors, and transistors into a small and compact package called a chip. This chip is about the size of the nail on the little finger. The chip is mounted in a plastic case with aluminum tabs that allow it to be mounted to a printed circuit board.
Radios consist of many specialized electronic circuits designed to perform specific tasksadio frequency amplifier, mixer, variable frequency oscillator, intermediate frequency amplifier, detector, and audio amplifier.
The radio frequency amplifier is designed to amplify the signal from a radio broadcast transmitter. The mixer takes the radio signal and combines it with another signal produced by the radio's variable frequency oscillator to produce an intermediate frequency. The variable frequency oscillator is the tuning knob on the radio. The produced intermediate frequency is amplified by the intermediate frequency amplifier. This intermediate signal is sent to the detector which converts the radio signal to an audio signal. The audio amplifier amplifies the audio signal and sends it to the speaker or earphones.
The simplest AM/FM radio will have all of these circuits mounted on a single circuit board. Most of these circuits can be contained in a single integrated circuit. The volume control (a variable resistor), tuning knob (a variable capacitor), speaker, antenna, and batteries can be mounted either on the printed circuit board or in the radio's case.
The Manufacturing Process
There is no single process for manufacturing a radio. The manufacturing process depends upon the design and complexity of the radio.
Manufacturers purchase the basic components such as resistors, capacitors, transistors, integrated circuits, etc., from vendors and suppliers. The printed circuit boards, usually proprietary, may be manufactured in house. Many times, manufacturers will purchase complete radio modules from an vendor. Most of the manufacturing operations are performed by robots. These include the printed circuit boards and mounting of the components on the printed circuit board. Mounting of the printed circuit board and controls into the case and some soldering operations are usually done by hand.
- The blank printed circuit board consists of a glass epoxy resin with a thin copper film cemented to one or both sides. A light sensitive photoresist film is placed over the copper film. A mask containing the electrical circuitry is placed over the photoresist film. The photoresist film is exposed to ultraviolet light. The photoresist image is developed, transferring the image to the copper film. The unexposed areas dissolve during etching and produce a printed circuit on the board.
- Holes are drilled in designated locations on the printed circuit board to accept the components. Then, the board is pre-soldered by dipping it in a bath of hot solder.
- Smaller electronic components such as resistors, capacitors, transistors, integrated circuits, and coils are installed in their designated holes on the printed circuit board and soldered to the board. These operations can be performed by hand or by robots.
- Larger components such as power transformer, speaker, and antenna are mounted either on the PCB or cabinet with screws or metal spring tabs.
- The case that houses the radio can be made either of plastic or aluminum. Plastic cases are made from pellets that are melted and injected into a mold. Aluminum cases are stamped into shape from sheet aluminum by a metal press.
- External components not mounted on the printed circuit board can be the antenna, speaker, power transformer, volume, and frequency controls are mounted in the case with either screws, rivets, or plastic snaps. The printed circuit board is then mounted in the case with screws or snaps. The external components are connected and soldered to the printed circuit board with insulated wires made of copper and plastic insulation.
Since most of the components or a radio are manufactured by specialized vendors, the radio manufacturer must rely on those venders to produce quality parts. However, the radio manufacturer will take random samples of each component received and inspect/test them to ensure they meet the required specifications.
Random samples of the final radio assembly are also inspected to ensure quality. The overall unit is inspected for flawsoth physical and electrical. The radio is played to ensure it can select radio frequencies it's design to receive, and that the audio output is within specifications.
Today's environmental awareness dictates that all waste be disposed of properly. Most byproducts from the construction of a radio can be reclaimed. The etching solutions used in the printed circuit board manufacture are sent to chemical reclamation centers. Scraps from the leads of electronic components are sent to metal waste recovery centers where they are melted to create new products.
Radios are being combined with computers to connect the computer to the Internet via satellites. Eventually radios will convert from analog to digital broadcasting. Analog signals are subject to fade and interference, digital signals are not. They can produce high quality sound like that found on a CD.
Digital radios can be programmed for specific stations, types of music, news, etc. Eventually, radios will have mini-computers built in to process sounds in numerical patterns "digits" rather than an analog waveform. This will allow listeners to program their radios for favorite radio stations, music type, stock quotes, traffic information, and much more.
Where to Learn More
Carter, Alden R. Radio From Marconi To The Space Age. New York: Franklin Watts, 1987.
Floyd, Thomas L. Electric Circuit Fundamentals. Columbus: Merrill Publishing Company, 1987.
The American Radio Relay League. The ARRL Handbook for Radio Amateurs. Newington, CT: ARRL, 1996.
Canadian Broadcasting Company Web Page. "The Future of Digital Radio.: December 2001. http://radioworks.cbc.ca/radio/digital-radio/drri.html>.
UC Berkley Web Page. December 2001. http://www.cs.berkeley.edu/~gribble/cs39c/Comm/radio/radio.... >.
Ernst S. Sibberson